Prepare for CMake2.8.12

Give Link-Type to target_link_libraries
Set Link-Type for Qt5 libraries
Use Qt4 moc code from cmake

This tries to use as much as possible from the CMake code
for execution of the moc command.

This way we can use the same customized code for CMake <2.8.12 and
>=2.8.12 again.
Use plain CMake Macros for UIC

We're now just unifing the name for Qt4/Qt5 (We had no modification
of the <2.8.12 UIC code).
Link-Type for Qt4 Libraries
Adjust RCC-Macro to workaround CMake 2.8.12 changes

Actually, this uses the unmodified CMake Macro on 2.8.12 and uses
our improved one with prior version of CMake. This is not ideal, but
changing established macros isn't either. I'd bet that if you'd ask
those guys, they wouldn't bother a second to argue that these macros
are meant to be private...
Merge pull request #16 from macgitver/feature/cmake2812

Add support for CMake 2.8.12